Audi diesel turbo boost loss of performance

[AudiAotearoa]

Hi there,
I have a 2005 3.0l diesel turbo Audi 4 Quattro that looses turbo boost from time to time when under load. When it does the glow light flashes and the performance is limited. When the car is restarted the glow light goes off and I have full power back. I have had our mechanic review the issue and they have produced the diagnostic report attached. They cant identify the what is causing the issue so have said they need to pull the turbo out to check it and it potentially may need replacing. The cost of the quote to that exceeds the value of the car so I would appreciate if anyone has had experience with this issue to please let me know how it was resolved? Any ideas on how I can fix it? Many thanks. Pete

 

[NHN]

Are those the actual codes or just suggested codes it may show up, as its got under & over boost, which maybe symptomatic of a boost controller, not sure on your engine if its a vaned turbo or electronically controlled.

 

[Sibmets]

Are those the actual codes or just suggested codes it may show up, as its got under & over boost, which maybe symptomatic of a boost controller, not sure on your engine if its a vaned turbo or electronically controlled.

On B7 its electronically controlled.
It's not uncommon for these to fail or intermittently fail, but they usually give a fault code.

Audi A4 B9 3.0 TDi quattro 200 kw